Add progress bar GIF to diffoscope.org.

index.html

@@ -56,6 +56,7 @@ layout: default
     them. It can compare two tarballs, ISO images, or PDF just as easily.
   </p>
   <div id="examples">
+    <img src="images/progressbar.gif?{{ site.time | date: '%s%N' }}">
     <div style="width: 438px;">
       <a href="examples/https-everywhere-5.0.6_vs_5.0.7.html">
         <img src="images/https-everywhere-5.0.6_vs_5.0.7.thumbnail.png?{{ site.time | date: '%s%N' }}" alt="Example of diffoscope HTML output" /><br />